In military operations, targets may be generally classified as either sheltered targets or sheltered targets. Unsheltered targets may be considered to include targets that are substantially exposed and vulnerable to weapons, including projectable devices fired by artillery directed at such targets. Such projectable devices include, without limitation, artillery shells and rocket-launched projectiles. For example, people, munitions, buildings and other fighting equipment that are openly located on a battle field and substantially exposed to the weapons of an enemy attack may be considered unsheltered targets.
However, many targets including, for example, people, munitions, chemicals, and fighting equipment may be sheltered in order to protect them from an attack by various weapons. Conventionally, a shelter for a target includes a physical barrier placed between the target and the location of origin of an expected enemy weapon in an attempt to frustrate the weapon directed at the target and prevent or mitigate the damage that might otherwise be inflicted by such a weapon. In some cases, targets may be heavily sheltered in an attempt to prevent any damage to a given target. In one example, one or more layers of concrete, rock, soil, or other solid material may be used in an effort to protect a desired target. Each layer may be several feet thick, depending on the level of protection desired. Sometimes these layers are referred to as shards layers, the term “hard” indicating a relative amount of resistance that they will impose on an incoming projectable device of a weapon system. Generally, a layer is considered to be “hard” when it exhibits a specified level of thickness, when it is formed of a material exhibiting a specified level of hardness or some other material characteristic which significantly impedes penetration of a projectable device, or when the layer exhibits a desired combination of material properties and physical thickness.
In order to penetrate shelters, and particularly a hard layer (or layers) of a given shelter, a weapon system using a projectable device configured with a penetrator system is conventionally used. The general goal of using a penetrator system is to breach the shelter, including any thick layers that may be present, and deliver the projectable device to a desired location (i.e., proximate the intended target) while delaying detonation of the explosive carried by the projectable device until it is at the desired locations. Thus, use of a penetrator system enables a more efficient and a more effective infliction of damage to a sheltered target and, sometimes, use of such a system is the only way of inflicting damage to certain sheltered targets.
A penetrator system is part of a weapon system that may employ one or more projectable devices in the form of warheads, a penetrator structure (generally referred to as a penetrator) and a sensor (such as an accelerometer) associated with and coupled to the penetrator. The penetrator may be configured to act as a warhead, or it may be a separate component, but generally includes a mass of relatively dense material. In general, the capability of a penetrator to penetrate a given layer of media is proportional to its sectional density meaning its weight divided by its cross-sectional area taken along a plane substantially transverse to its intended direction of travel. The weapon system may include equipment for guiding the projectable device to a target or, at least to the shelter, since, in many cases, forces associated with impact and penetration of a shelter may result in the removal of such guidance equipment from the penetrator portion of the projectable device. The sensor of a penetrator system is conventionally configured to assist in tracking the location of the penetrator as it penetrates layers of one media type or another after an initial impact of the weapon projectable device and, thus of the penetrator, with the shelter.
Various conventional penetrator systems have been employed with some degree of success. In some conventional penetrator systems, a sensor is used to detect an initial impact with a structure. The system then monitors the amount of time that has elapsed subsequent to the detected impact in an effort to keep track of the location of a penetrator, based on calculated or estimated velocity of the weapon, as the penetrator penetrates a shelter. Such systems are sometimes referred to as time-delay systems.
Other conventional penetrator systems utilize one or more sensors, such as an accelerometer, to measure the deceleration of the penetrator. The system then tracks the distance traveled by the weapon, from the time of the initial impact with a layer of a shelter or structure, in an effort to determine the projectable device's projected location with the shelter or structure. These systems are generally referred to as penetration depth systems.
Some conventional penetrator systems utilize an accelerometer to detect deceleration of the projectable device responsive to contact with relatively hard and/or thick layers in an effort to help count the layers of media, count voids between the layers of media, or count both media layers and voids so as to determine the projectable device's substantially instantaneous location within a particular structure.
Such conventional penetrator systems provide an output signal for initiating explosive or other energetic material carried by the projectable device after the penetrator system has determined that the projectable device has arrived at a desired location within the shelter. Desirably, the initiation of the explosive or other energetic material occurs at a target site, such as within a specified room of a bunker. However, in practice, any of a number of factors may result in the miscalculation of a projectable device's projected location within a shelter and, therefore, initiation of the explosive or other energetic material at an undesired location. Such factors may include, for example, variability in the physical or material characteristics of a given layer.
One particular issue faced by conventional penetrator systems includes the ability to detect so-called thin layers. While penetrator systems have been used to detect decelerations that result from contact of the projectable device with a relatively thick or hard layer, such penetrator systems have not been effective in accurately detecting and, thus accounting for, layers that are thin, soft, or some combination thereof, due to the relatively low amount of deceleration experienced by the projectable device when passing through such thin or soft layers. Some examples of “thin” layers include ceilings and floors in buildings that may be located over a target. Some examples of “soft” layers include layers of sand or other soft soil. Generally, a layer is too thin or too soft to detect when the deceleration of a penetrating weapon, as it passes through such a layer, cannot be discriminated from electrical noise, mechanical noise, or a combination of electrical and mechanical noise experienced by the sensor. Therefore, there is a desire to eliminate isolate or reduce noise experienced by a penetrator sensor in order to provide better reliability of and indication from the sensor signal, regardless of the characteristics of material layers (a thick, thin, hard or soft, including voids) encountered by the projectable device.
Some conventional penetrator systems have utilized gain switching in an effort to detect relatively thin layers. Cain switching generally includes use of a high gain amplifier to detect low levels of deceleration by the projectable device and use of a lower gain amplifier as deceleration of the projectable device increases. Such gain switching may occur between a computer sampling of the projectable device's deceleration. Gain switching may generally be accomplished using one or more amplifiers, one or more analog-to-digital converters, or some combination thereof. Nevertheless, such systems are less effective in detecting layers that are of a thinness exhibited in numerous targets such as the thin roofs and floors of many buildings because the signal, although amplified, must still be discernable over noise, such as impact amplification noise. Therefore, it is also desirable to reduce noise to a sensor to improve the sensitivity of penetrator systems.
Some conventional penetrator systems have actually attempted to avoid detection of thin layers so that the attendant errors in detecting soft or thin layers do not “confuse” the system and result in the untimely initiation of the explosive or other energetic material carried by the projectable device. For example, some attempts have been made to adjust the sensor thresholds of a penetrator system so that they only detect so-called “hard” layers and effectively ignore all thin or soft layers of a shelter. However, such attempts unfortunately result in the sensor ignoring a layer that may be significant to a well-timed detonation such as, for example, the ceiling of a hunker, again resulting in the detonation of the energetic material carried by the projectable device at an undesired location.
In other conventional penetrator systems, attempts have been made to not only ignore thin layers, but to prevent the system from erroneously counting a single layer as more than one layer. To do so, such penetrator systems have used a programmed distance, sometimes referred to as a “blanking distance,” to ignore both false layers and real layers after the penetrator system has detected a deceleration of the projectable device. In one example, a conventional penetrator system would calculate and measure the blanking distance traveled by the projectable device based on the penetration velocity of the penetrator system at the time of its impact with a layer and the time that expired after such impact. Some other penetrator systems have also used the deceleration values and the detection of an exit of the projectable device from a penetrated layer to help determine the blanking distance.
Yet another system entitled “Method for detection of media layer by a penetrating weapon and related apparatus and systems,” by one of the inventors herein, published May 4, 2006 as United States Patent Application number 20060090662, the disclosure of which is incorporated by reference herein, provides a method of locating a penetrating-type weapon within a shelter. The method includes projecting the projectable device through a layer of media and detecting a weapon frequency induced by vibration of the projectable device. A harmonic frequency of the weapon frequency is analyzed to determine, for example, whether a deceleration event has occurred. Analysis of the harmonic frequency of the weapon frequency may include determining whether the amplitude of the harmonic frequency meets or exceeds a defined minimum amplitude. In order to improve the robustness and accuracy of determining the amplitude of the harmonic frequency determined, a sensor of a penetrator system, for example, an accelerometer, would benefit from improved vibration, acceleration and deceleration sensing while being less susceptible to noise caused by impact or penetration shock amplification. Therefore, there is a further desire to improve vibration or acceleration sensing by providing a sensor of a penetrator system that is less susceptible to impact or penetration shock amplification.
What has been observed of penetrating weapons configured as projectable devices during testing is that the impact and penetration of the projectable device, may result in a shock capable of degrading or destroying the accelerometer, electronics, explosive initiators and explosives in the fuze or fuze well. It is further contemplated that the impact and penetration shock, experienced by the projectable device, mechanically amplifies the acceleration effect upon the accelerometer or sensor. Therefore, it is an additional desire to provide an attachment that efficiently locks, reliably loads and robustly secures a sensor, such as an accelerometer, of an installable fuze into a fuze well of a projectable device in order to minimize shock amplification in the accelerometer at impact and during penetration of a projectable device into a desired target.
Accurate detection and recognition of soft, hard, thin or thick layers is desirable in many applications using an installable fuze having a sensor and associated electronics therein. As such, there is a continued desire to improve the penetrator systems used in projectable devices of weapon systems so as to increase their accuracy in determining their arrival at a desired location by eliminating or reducing noise affecting the sensor's detection capabilities, particularly caused by mechanical amplification experienced at impact and during penetration.
Accordingly it is desirable to eliminate, isolate or reduce the noise experienced by the sensor in order to provide better reliability of and indication from the sensor signal, regardless of the projectable device passing through a thick, thin, hard or soft material layer (including voids). It would also be of advantage to reduce noise to a sensor to improve the sensitivity of penetrator systems. Of further advantage would be to improve vibration or acceleration sensing by providing a sensor of a penetrator system for use in a projectable device that is less susceptible to impact or penetration shock amplification.